In this case the mineral breaks with a curved concav convex surface as in case of quartz, opal, flint etc. The subconchoidal is used to describe less devel conchoidal fracture.
The fracture surface is flat as in case of chert.
The fracture surface is rough due to minute elevations depressions as in case of feldspars etc. It is the common variety of fracture seen in case of majority of minerals.
The fracture surface is studded with sharp elevations as case of sillimanite.
ADVERTISEMENTS:
Specific gravity:
The specific gravity of a mineral is the ratio of weight of the mineral to that of an equal volume of water. In selecting mineral for determination of its specific gravity the sample should be and free from alteration products and inclusions.
The specific gravity mineral depends on the atomic weight of the constituent elements and manner in which the atoms are packed in the crystal structure. For ex with similar crystal structure Celestine (SrS04), barite (BaSOJ anglesite (PbS04) have specific gravity values of 2.9, 4.5 and 6.3 respectively. The influence of the manner of packing on the specific gravity is discernible in case of carbon minerals like graphite and diamond.
Graphite with loose packing has specific gravity 2.3 while diamond with close packing has specific gravity of 2.54. Generally the non-metallic minerals have specific gravity of about 2.6 – 2.8 where as the metallic minerals have specific gravity about 5 or more. However, there are some exceptions. The specific gravity of the minerals can be accurately determined by chemical balance, Walker’s steelyard balance, Jolly’s spring balance, pycnometer or specific gravity bottle and by heavy liquids.
ADVERTISEMENTS:
The specific gravity of a mineral can also be expressed in a relative sense by using words like low, moderately low, high and very high with specific gravity values of less than 2.5, 2.5 – 3.5, 3.5 – 7 and more than 7 respectively.
Special properties: Special properties of the minerals are taste, odour, feel, tenacity, diaphaneity and properties based on magnetism, electricity, radioactivity and acid reaction.
Taste: The water-soluble minerals have some characteristic tastes. The tastes given in are noteworthy.
Odor:
ADVERTISEMENTS:
Some minerals have characteristic odour that comes out with mineral is blown with mouth, rubbed or heated. These are given in Table.
Earthy: Kaolin, bauxite when blown by mouth
Sulphurous: Sculpture, pyrites when struck, sulphides when heated
Garlic / alliaceous: Arsenic minerals when heated
ADVERTISEMENTS:
Foetid (rotten egg smell): Limestone and some quartz when heated
Feel:
Some minerals have characteristic feel as given in,
Characteristic feel of certain minerals
ADVERTISEMENTS:
Feel Mineral Feel Mineral
Greasy: Graphite Smooth: Galena
Soapy: Talc, chlorite Rough: Bauxite
Some minerals like graphite and psilomelane mark the paper and blacken ti
ADVERTISEMENTS:
Tenacity:
Some minerals have definite properties dependent upon tenacity. These are given in.
Tenacity property of certain minerals Property Mineral
Sectile: The mineral can be cut by a knife; e.g. graphite, gypsum, stea’
Malleable: The mineral flattens under hammer; e.g. native gold, silver and c
Flexible: The mineral can be bent; e.g. talc, selenite
Elastic: The mineral restores its original position after being bent; e.g. mica fl’
Brittle: The mineral when struck yields powder instead of slice?
Diaphaneity:
Diaphaneity refers to the amount of light transmitted through the minerals. Depending on the amount of light transmitted, the following terms given in.
Electrical properties:
Native metals like gold, silver and copper electricity. Graphite, though a non-metal, is good cond electricity. Some minerals like tourmaline develop electric ch different parts when heated up.
Such minerals are known as pyr When heated up, the crystal becomes negatively charged at its s and positively charged at its blunt end. When subjected to pressure, minerals like quartz become electrically charged. This effect is known piezoelectricity.
Radioactivity:
Minerals containing elements of high atomic weigh as uranium, thorium, radium etc are radioactive. They emit arrays in different quantities. Minerals like uraninite and monazi radioactive minerals.
Reaction with acids:
Some carbonate minerals like calcite, are galena, sphalerite and dolomite (when finely powdered) react with such minerals are readily identified in the laboratory by their r property. Some of the minerals like sylvite, halite are soluble in HN few other minerals are also soluble in H, SO, or HF.